Quoted: A survey of the workers confirmed what the plant’s nurses had suspected: those who got sick were employed at or near the “head table,” where workers cut the meat off severed hog heads.

On Nov. 28, Dr. DeVries’s boss, Dr. Ruth Lynfield, the state epidemiologist, toured the plant. She and the owner, Kelly Wadding, paid special attention to the head table. Dr. Lynfield became transfixed by one procedure in particular, called “blowing brains.”